The invention relates to an apparatus for examination of chemical and/or biological samples by means of optical devices. Such an apparatus can be provided e.g. as a microscope, particularly a confocal microscope.
Apparatus for examination of the above type comprise an objective for observation of the sample. When the objective is used, for instance, to observe a sample arranged in a sample support from below through a sample carrier bottom which is transmissive to the respective observation radiation, the given constellation of the refractive indices will have an unfavorable effect on the course of the path of rays, particularly in case of high numerical objectives. Varying refractive indices occur in the transition regions between the exit lens of the objective and the ambient air, as well as between the bottom of the sample support and the medium arranged between the objective and the sample carrier bottom.
Particularly in confocal microscopes which are used in high throughput screening, the focus has to be very small. This is required since, in high throughput screening, examination is performed on samples having low volumes in the μl range or below. Since the amount of the radiation emitted by the sample and taken in by the objective (collection efficiency) has a considerable influence on the measurement time, the aperture of the objective has to be as high as possible. This is of importance particularly in high throughput screening because the measurement time is one of the decisive parameters.
Normally, by use of a pipette or the like, the immersion liquid is applied manually to the exit lens of the objective with a refractive index >1. Particularly in high throughput screening systems and fully automated microscopes and the like, this is extremely cumbersome because the objective is arranged at a small distance to a sample support such as a titration plate. For applying the immersion liquid, the objective has to be retracted downwards so that the user can apply immersion liquid onto the exit lens by means of a pipette or the like. Subsequently, the objective is advanced to the sample support again until the gap between the exit lens of the objective and the outer surface of the sample support has been filled with the immersion medium. Alternatively, the objective can be stationary and the sample support can be moved.
A further disadvantage resides in that, when examining samples in titration plates, i.e. in sample supports comprising a plurality of individual samples, a relative movement will occur between the objective and the titration plate because the objective has to be advanced to each individual sample or vice is versa. In this relative movement, part of the immersion liquid will always remain on the underside of the sample support so that, after examination of several samples, the gap between the exit lens of the objective and the outer surface of the sample support may not be filled completely with immersion liquid anymore.
It is an object of the invention to facilitate the provision of immersion liquid in optical examination apparatus.